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string_concatenation.rb
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string_concatenation.rb
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# frozen_string_literal: true
module RuboCop
module Cop
module Style
# This cop checks for places where string concatenation
# can be replaced with string interpolation.
#
# @example
# # bad
# email_with_name = user.name + ' <' + user.email + '>'
#
# # good
# email_with_name = "#{user.name} <#{user.email}>"
# email_with_name = format('%s <%s>', user.name, user.email)
#
class StringConcatenation < Base
include Util
extend AutoCorrector
MSG = 'Prefer string interpolation instead of string concatenation.'
def_node_matcher :string_concatenation?, <<~PATTERN
{
(send str_type? :+ _)
(send _ :+ str_type?)
}
PATTERN
def on_send(node)
return unless node.method?(:+)
return unless string_concatenation?(node)
topmost_plus_node = find_topmost_plus_node(node)
parts = []
collect_parts(topmost_plus_node, parts)
add_offense(topmost_plus_node) do |corrector|
corrector.replace(topmost_plus_node, replacement(parts))
end
end
private
def find_topmost_plus_node(node)
current = node
while (parent = current.parent) && plus_node?(parent)
current = parent
end
current
end
def collect_parts(node, parts)
return unless node
if plus_node?(node)
collect_parts(node.receiver, parts)
collect_parts(node.first_argument, parts)
else
parts << node
end
end
def plus_node?(node)
node.send_type? && node.method?(:+)
end
def replacement(parts)
interpolated_parts =
parts.map do |part|
if part.str_type?
if single_quoted?(part)
part.value.gsub('\\') { '\\\\' }
else
escape_string(part.value)
end
else
"\#{#{part.source}}"
end
end
"\"#{interpolated_parts.join}\""
end
def single_quoted?(str_node)
str_node.source.start_with?("'")
end
end
end
end
end